@GeneralVan: Does Kagato have his ship?
Factoring in powerscaling (would have to in this case since Kagato doesn't have much impressive showings for actual feats otherwise), Kagato would be stronger than Ryoko as he is capable of drawing upon more power from the gems aboard his ship than Ryoko can presently draw from her gems and possesses a mostly similar power set as the space pirate and Ryoko was at least planet-busting level considering her mother's gems give her the capability to pierce through Light Hawk Wings, as seen against Z. Regardless of form, Madara's screwed here.
@GeneralVan: Fail to see what that has to do with the battle. Kagato was capable of subduing Ryoko when they met again in episode 5 of the OVAs and he was clearly having the advantage aboard the Soja during their fight with one another before tapping into his ship's gems. Before you go saying "but Washu said Ryoko was holding back", Washu was unaware of the advances in Kagato's power during the thousands of years she was sealed in the Soja's reverse world. I fail to see anyone in the HST capable of denting him in singles combat.
Kagato has why better intangibility and instant regeneration. besides he beat Washu who even in normal form is way out of Ryoko's league and Washu has always been the top of the food chain. I think Kagato will have a difficult time but he would still win in the end, but I think Madara the sage could win in theory if he can hit Kagato while he is intangible with the black orbs.